Brake lining



Novyz4, 1936. A DT 2,051,919

BRAKE LINING Original Filed Oct. 351, 1951' l NVENTOR W/zu/W NAN/Z7. 0r

BY ATTORNEY a greater outlay of capital and involving various Per cent difliculties in handling and distribution. Asbestos 30 to 60 One of the important objects of the present Rubber 10 to 20 20 invention is to provide a molded type of brake Sulphur to mung whmh possesses 'sumcient flexibmty to I also utilize in conjunction with the above in- Fig. 4 is a detail showing the manipulation of in the process. 55

I Patented Nov. 24, 1936 Q UNITED STATES PATENT" orrica BRAKE LINING William Nanfeldt, cumin, N. 1., assignor to World Bestos Corporation, Paterson, N. J., a corporation of Delaware Application October 31, 1931, Serial No. 572,345

Renewed April 22, 1936 9 Claims. (01. 154-52) This invention relates to molded brake lining the friction strip to bring about a transverse curvand other fibre containing products. The invenature of the same. tion is directed toward a product particularly suit- As hereinabove stated, this invention has parable for brake band purposes which possesses a ticular utility when employed in the formation 5 hardness and durability of the molded product ofproducts such as frictional brake lining which 5 while at the same time it has flexibility sufficient contain fibre such as asbestos. In my copending to permit application on brake drums of varying applications, Serial No. 429,922, filed February 20, diameter. 1930, and Serial No. 512,892 filed February 2, 1931, Heretofore, brake lining of the molded type has I have described compositions containing rubber 10 usually had the disadvantage of being inelastic so and asbestos, which may be molded into satis- 10 that its manufacture necessitated curving the factory brake lining. As stated in these applicabrake lining to fit the brake band of'the particutions, more particularly in application Serial No. lar automobile for which the brake band was 'in- 512,892, of which this application is a continuation tended, This necessitated also that the jobber and in part, I prefer to use the following ingredients 15 dealer keep on hand in stock a multiplicity of difin the percentage ranges by weight of the com- 15 ferent sizes and shapes of brake band, requiring pleted composition as follows:

1% 33 gfi fi zfii i' gg 3:35; gredients, the following 'materials in varying proportions at the same time possesses a high degree of hardl Per cent 5 ness' and durability as compared with other stand- Gm h p ite -r Ho 6 ard commercial types of brake lining. Litharge 1 to 10 Another object also, is to provide a lining which Iron 1 to 5 possesses the advantages of laminated structure Kaolin 1 to 25 without having physical separation of the lamif nations. A satisfactory composition contains percentages 30 Another object is to provide a brake lining by weight of the completed composition as folwhich will not fracture normally through its comlows: l plete mass, but will fracture in sections of the Per cent thickness. Stillanother object is to provide a Asbestos fibre- 45 brake band lining containing asbestos fibre and Rubber. 18 35 rubber in which the asbestos fibre is generally Sulphur 9- parallel to the plane of the surface strip and in Magnesium owide- 3. 6 layers through the strip. Graphit 6 Another object of the invention is to provide a Litharge 6 40 type of molded brake lining which when adjusted Iron ovide 3 40 to a brake shoe, will lie fiat thus permitting a Kaolin- 9. 1.

fi zfi gggz gfigg zgz The composition containing these ingredients above and other objects are accomplished by the itg ggggig fi f zfigzg 5 3 32 22 friction material hereinafter described in detail prefer the method described in my copendi'ng p 45 and'refemd m the accmpa'nymg drawing in plication, serm No. 512,892.

'which- Y According to this latter method, crude smoked 5356 is a perspective of a section of a friction rubber'sheets are macerated between oppositely travelingrolls in a roll mill, and simultaneously Fig. 2 is a perspective of a friction material in I strip formcurved. for applicationto a br k shoe combined with certain cure accelerators, such as or drum; magnesium oxide (MgO) and litharge in the pro- Fig. 3 is a section through the strip of Fig. 2; portions herelnabove mentioned. Sulphur is also and added to bring about vulcanization in a later step The macerated rubber is then placed in thin sheet form, the sheets having a thickness preferably less than one-thirty second of an inch, four or five thousandths being as satisfactory. This 6 sheet of rubber mixture is then placed in a masticator or mixing machine of the impact type having rotating blades or impact members which constantly carry around and agitate the contents of the material. To the rubber is added a rubber l solvent, such as gasoline, benzol, solvent naphtha, etc., the weight of the solvent being approximately that of the batch of material.

The rubber and solvent are mixed for approximately half an hour, oruntil the rubber becomes 15 'a cement, and asbestos fibre in the proportions above stated is then added and mixing continued until individual fibres of the asbestos are coated with the cement. This step is important as the rubber acts as a protective coating for the 118-,

After about half an hour when the as- .0 bestos.

bestos has been thoroughly coated, rubber latex is added in amounts varying from 1% to 75%'-of the predetermined quantity of rubber to be used in the completed composition. The latex is mixed 25 with the coated asbestos until it is absorbed in the mixture. Then the final filler, lubrication, and cure elements are added such as iron oxide (FezOa)', graphite, and kaolin, and these elements thoroughly stirred and mixed into the batch until 30 a homogeneous mixture is obtained.

The mix is now transferred to a second roll mill which may have one roller corrugated and which serves to further macerate and rend the material, and also to crush all small masses or balls of the I 35 mixed material so that a smooth, uniform and homogeneous stock is finally obtained suitable for insertion inthe extruder or for any other purpose for which a moldable composition may be used.

In utilizing the composition as has been de-- 40 scribed hereinabove, the material is placed in a hydraulic press of suitable form which is provided with a nozzle or outlet with a flat mouth so that the extruded material as it emerges from the mouth is approximately in the strip form desired 45 with such excess dimensions as will allow for shrinkage in the curing operation as well as for grinding operations which may be necessary to properly smooth the surface of the material.

As described in my copending application Serial 50 No. 512,892, the extruding apparatus is provided with a screening plate adjacent its outlet to remove foreign material and to align the fibres of the asbestos where asbestos is employed. The nozzle of. the extruder is also provided with parti- 55 tions, the faces of which are parallel to the flat side of the strip and serve to divide the strip into a plurality of fiat sheets which later recombine, and the material subsequently emerging a a gle undivided layer. This temporary division in w the nozzle removes the fibre from the internal surfaces where recombination of the strips is made and in the completed product enhances the flexibility of the brake lining. 1

After emergence fromv the extruder, the material in strip formis passed through adrying oven of standard form including an enclosure in which heat is applied to cause evaporation of the solvent.

- An important advantage ofthe use of latex bea comes evident in this drying operation inasmuch as is the case where crude rubber alone is used in-the preparation of the composition, the surface of the strip when dried first forms a hard and impervious skin layer which effectively hinders evaporation of the solvent from the interior of the 5 strip, and thus very materially increases the time necessary for removing the solvent. By using rubber latex composition, the drying time is reduced over 50%, the actual reduction being from four-to five hours toone to two hours While the use of anenclosed oven with the application of artificial heat is preferable as hastening the drying operation, it would be feasible to dry the strip in th open air provided the humidity and temperature conditions were suitable.

From the drying oven the strip is conveyed to a calendering or forming roll preferably of the type where oneroll has projecting rims or edges while the other roll is without rims, the second roll compressing the material between the rims of the first roll.

After the rolling operation whichperceptibly diminishes the thickness of the strip, the strip is then-subjected to an edge grinding operation. This is done by standard equipment such as two opposed flat plates coated with friction material and rotating in opposite directions. The edges of the strip are, by this means, rendered smooth and all dried and wrinkled portions removed.

The strip is then ready for the vulcanizing step.\ This-may be accomplished in various ways but a! satisfactory method is the use of the well known fiat press consisting of a channeled surface in which the strip material is adapted to be inserted and a press element adapted to fit in the channels over the strip to compress th same, preferably to pressures of approximately 1500 lbs. persquare inch. This pressure is ordinarily applied for fifteen minutes while the press is being maintained at a temperatureof 325 F. vulcanization occurs under these conditions of heat and pressure, leaving the substance in a rigid condition with a hard surface skin.

In order to place this rigid strip in condition for brake lining or other frictional purposes and impart a good degree of flexibility to it, it is necessary that one face at least of the cured brake lining be removed, and this may be done by an ordina y grinding wheel having an abrasive surface with suitable guiding wheels or pulleys to maintain the material in position. By this means irregularities in the dimensions of the strip are removed.

A final operation employed in the treatment of this brake lining in order to insure the necessary 5 .fiexibility consists in passing the strip through rollers'lll, l l and I2. The roller i0 has a surface which is convex inaxial section; the roller H has a surface which is concave in axial section, while the roller 12 is straight in axial section. It is apparent, therefore, that when the strip is passed about the convex roller l0 that it will receive a slight curvature, giving the product a slight bevel or crown on its outer surface. The flexing of the material also serves to loosen the 85 fibre and give the completed product a maximum of flexibility without in any way modifying the intrinsic hardness of the substance. Thecrown on the surface of thestrip makes it possible to adjust the strip when used as a brake lining, to various diameters of brake shoes so' that when secured in position the lining lies fiat rather than curved as would be the. case when the lining is made fiat and 'then curved to fit'the brake shoe. Consequently the-transverse curvature of the II lining as above described insures a true flat surface of application to the brake drum.

The inherent flexibility of the brake band results from its layer construction, which through causing a horizontal positioning of the fibrous stock of the material, tends to permit more readily a lateral movement of the lining. This advantageou's characteristic of the completed brake band is brought out in Fig. 1, where the various layers or laminations are indicated by the numeral I3 and as separated by imaginary planes i4. While, of course, there is no separate movement of these-individual layers of material in the brake lining, in each layer the fibres are more or less parallel to' the surface of the brake band and hence will not tend to restrain a lateral flexing of the band.

Another feature of the invention as brought about by the layer construction, will be apparent on consideration of the fact that lumps or balls of the stock cannot exceed in the finished product the width of an individual layer. when the band is subjected to a sharp bending movement, there can be no point of weakness in the band induced by the presence of a ball or lump of conglomerated material. Should any small lumps of the material enter into the finished product, a fracture of the band resulting therefrom would extend only to one layer.

Because of the flexibility of the brake band brought about by its layer construction and by its subsequent treatment to edge grinding and surfacing, it is possible for the manufacturer to ship the lining in roll form directly to the jobber or dealer, who may then cut thelining to length and fit it to a brake drum of any make of automobile having diverse curvatures. This is an advantage of highestimportance, resulting from the invention.

In addition to the flexibility arising from the laminated construction, the hardness and durability of the lining is augmented. Brinell hardness tests on the lining surface give a reading of eight-thousandths of an inch with a threequarter inch slug, using a pressure of 3000 kilograms as compared to twelve to fifteen thousandths for competitive linings.

'While' I have described in general terms the process for making friction material, it is of course understood that various alterations may,

be employed in the steps involved. Instead of a press, I may, surface of the curved strip. I may also modify thefibrous stock which may be either vegetable or mineral including cotton, wool, hemp, shredded leather, etc. although the invention has special utility inthe formation of brake band lining from a moldable composition containing asbestos.

Hence,

for example, grind more than one 'wish to be restricted except as required by the claims hereto appended. 4

Having thus described my invention what I- desire to claim is:'

1. A molded-brake lining containing asbestos fibre and a homogeneous bonding agent, there being planes within said lining parallel to a surface plane thereof through which asbestos fibres do not extend'transversely.

2. A molded brake lining consisting of asbestos fibre and other filler and binding substances, the asbestos fibre lying in separate layers in said lining and in similar alignment.

3. A brake band lining consisting of a plurality of separated layers of asbestos-containing material and bonding material substantially free of asbestos fibres in which said layers are embedded, said lining being curved in transverse section.

4. A brake band lining comprising a plurality of separated layers of asbestos-containing matecontaining material and bonding material substantially free of asbestos fibres in which said layers are embedded, said surface curving outwardly from the edges thereof, relative to the center of curvature of the lining.

6. A brake lining formed of a molded product, said lining being in strip form, one of the main surfaces of said strip being ground smooth and curvilinear in transverse section.

.7. A brake band consisting of a strip of homogeneous body material and material containing fibrous stock positioned in layer formation in said body material, the fibres of said stock being positioned in general in planes approximately parallel to the surfaces of said layers.

8. A brake band consisting of a strip of homogeneous body material and material containing fibrous stock positioned in layer formation in said body material, the fibrous stock of each layer being confined to said layer and lying approximately parallel to the surfaces of the layers.

9.v A brake band consisting of a strip of homogeneous body material and material containingfibrous stock positioned in layer formation in said body material, said fibres being aligned approximately parallel to the layer surface. 

